This invention relates to a cyclic and upward water jet type automatic ice making machine or apparatus. More particularly, it relates to an improvement in such machine or apparatus according to which ice cubes formed in respective cells of the freezing chamber are separated from one another when formed and are of a regular shape free of connecting portions and the state of termination of ice formation and the state of termination of harvesting may be positively achieved without regard to ambient temperature or other factors.
In FIG. 1A, there is shown a typical freezing chamber of the prior art apparatus. A number of chamber partitioning plates 2 formed of copper are welded to a freezing grid or chamber 1A formed of copper so that a large number of freezing grids are formed. Ice-making water is directed in jet upwardly towards the freezing grid for forming ice cubes 5 in the respective cells 3. FIG. 10 shows the ice cubes separated from the chamber 1.
In such a conventional system, both the freezing chamber and the partitioning plates are formed of a material of relatively high thermal conductivity. Hence, the free edges of the partitioning plates 2 are cooled to an ice-forming temperature so that some time interval elapses before the return water falls from this area as droplets. Moreover, this edge area 4 of each partitioning plate 2 is contiguous to the adjacent cell and the return water falling down both sides of the partitioning plate is united at the edge area of each partitioning plate 2. The result is that a thick ice layer is formed at the edge zone 4 of each partitioning plate 2. When the freezing chamber 1 is switched to harvesting, each ice cube 5 is connected to an adjoining ice cube by a connecting portion 6, and the ice tends to hang down in an icicle shape, thus making it difficult to achieve uniform ice cube shape and considerably detracting from the commercial value of the ice cubes. The ice cubes thus connected together do not separate into individual ice cubes solely from the impact caused by the ice cubes falling into the storage bin. This disadvantage proves to be fatal especially when the ice making machine is incorporated into an automatic ice cube vender in which a preset amount of the ice cubes is to be dispensed from the storage bin.
As a means for separating the thus connected ice cubes into individual ice cubes, it is known to use a cord heater (not shown) suitably connected with the aid of a heat insulating frame for melting and cutting the connecting portions of the ice cubes. However, this known system is inconvenient because of its excessive consumption of electrical power and difficulties in assemblying, servicing and maintaining cleanliness.
As a means of sensing the end of ice making, it is known to use a timer or a temperature sensor such as a thermostat or thermister for sensing temperature changes in the freezing chamber.
With these known means, the ice formed in the ice making machine is affected by changes in the ambient temperature both in the quality and the amount of the ice, thus making it necessary to provide an automatic device for adjusting the timer setting or temperature characteristics of the sensor. As a result thereof, the maintenance operation tends to be complex and the manufacturing costs are also increased. The end of harvesting can be detected by sensing temperature changes in the freezing chamber by temperature sensors, such as thermostats or thermisters. However, in general, these sensors are supplied as separate items from the sensor for sensing the termination of ice forming, thus further raising manufacturing costs.